Electrochemical processes and more specifically the electrocoagulation process are known since 1906, when A. E. Dietrich patented the first electrocoagulation process for the treatment of bilge oily water from ships. Treatment of wastewater by electrocoagulation has been practiced for most of the 20th century with increasing popularity. In the last decade, electrocoagulation has been increasingly used in the United States, South America and Europe for the treatment of industrial wastewater containing metals. In North America, electrocoagulation has been used primarily to treat wastewater from pulp and paper industries, and mining and metal-processing industries. Recently, electrocoagulation was applied to treat wastewater containing food wastes, oily wastes, dyes and ink, chemical and mechanical polishing wastes, organics in landfill leachates, and effluents containing fluoride and synthetic detergent.
Current electrocoagulation devices are typically used in combination with additional devices performing required steps of the purification process such as contaminant coagulation, flocculation, and separation from the treated effluent.
Limitations of electrocoagulation, as it is performed today and that prevent it from wide commercial use for treating contaminated wastewater such as sewage, bilge water, and industrial wastewater include, for example, passivation of the electrode surfaces; inability to treat concentrated wastewater without a large number of electrodes or high electrode surface areas and long hydraulic residence times, due to the need to use low current densities to prevent passivation in the absence of continuous electrode cleaning mechanisms; build-up of sludge inside the treatment vessel leading to blockages and short circuits, which requires stopping the process in order to clean the vessel; inability to operate on marine vessels due to vessel motions such as vibration, roll and pitch which can affect hydrodynamics and alter the electrocoagulation process efficiency; inability to maintain a constant and small inter-electrode gap in order to operate at a constant and low voltage; inability to treat the entire wastewater stream due to hydraulic short circuiting or dosage of only a portion of the stream with the electrolytically-generated coagulant, and necessity to add one or more unit operations after the electrocoagulation process in order to complete the desired wastewater treatment and separate purified wastewater from contaminants.
There is still a need in the art for an optimized device for electrochemical wastewater purification.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.